#define  _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <math.h>
int yang(int n)
{
	if (n == 1 || n == 2)
		return 1;
	else
		return yang(n - 1) + yang(n - 2);
}
int main()
{
	int month = 0;
	scanf("%d", &month);
	printf("%d", yang(month));

	return 0;
}